In an ideal world, we could perfectly balance all rotating devices without vibration. Unfortunately, this is not yet possible, and fans are similar to all rotating devices in this aspect. Depending on the level of the balance and the speed of a fan, there will be a certain level of vibration generated by fan products.
Isolation between a fan and a structure which the fan is mounted on should be considered in every system of designs to reduce the fan vibration. Also, any possible resonances between the frequency of a rotation of a fan and its mounting structure should be considered. We have seen situations where these resonances created up to an additional acoustic noise at the system level.